Gravity is put together quite well in terms of pacing, and it ends exactly where it needs to end. However, it left me with some questions that will never get answered...
1) Could Houston hear their transmissions, or was communication completely cut off? This is an interesting question to me because it changes the dynamic of what was going on at Houston at the time. If they can't hear anything and can't send anything, they're running around like chickens with their heads cut off, desperately trying every trick in the book trying to reconnect and hoping for the best. It becomes this very technical issue. But if they can hear Stone and Kowalsky, then it becomes this very human drama, because yes, they're trying to reestablish communication, but they're essentially listening to two people die and there's nothing they can do about it.
2) On the above note, one piece of evidence that supports a total communications blackout is when Stone plummets to Earth in the capsule, and the messages she hears are being sent in multiple languages and at no point do they ask for her by name...which means they completely have no fucking idea who's in there. Which also means that Stone is not the only astronaut that is missing. There's a good chance the other Soyuz capsule never made it back to Earth safely.
3) Considering that they pretty much destroy everything of importance in orbit, it's safe to say that the space program is completely boned after this incident. Wouldn't that be an interesting movie or TV show, where they're trying to rebuild... not saying I want a sequel, but the story ideas are intriguing (and I hear, the plot of Planetes, which I guess I should read now).
4) They better give Kowalsky the record for longest spacewalk. Just sayin'. Officially, his time of death really should be recorded as when Ryan saw him, even if it was just a hallucination (and I loved that the movie was very coy on that part, appeasing both spiritual and non-spiritual people alike).